In the past the human fetus has for many years remained a medical mystery while existing in its mother's womb. Now fetal anatomy, normal and abnormal, can be accurately defined by a process called ultrasonography. This investigative process uses ultra-high frequency sound waves which are passed through the mother and fetus with return echos displayed on a cathrode ray tube showing the internal component structures of the bodies.
Until recently, the only question raised by any prenatal diagnosis of a fetal malformation was whether to abort the fetus or allow it to proceed full term with possible malformity. In some cases where these malformations are recognized too late for safe abortion, the only alternative is to provide appropriate postnatal management upon birth.
With the innovation of ultrasonography and the further development of this process to its present high level, it is now possible to recognize fetal hydrocephalus much more frequently because the fluid-filled cavities are particularly easy to detect by this method. A rather simple lesion which obstructs the passage of fluid from ducts in vital portions of the fetus can produce devastating pressures that can dilate various organs or cavities. This excess fluid pressure and dilation can greatly restrict the normal development of critical organs. One of these malformities is obstructive hydrocephalus secondary to stenosis of the aquaduct of Sylvius. In this abnormal situation the restriction of the flow of fluids from the ventricles within the brain of the fetus can produce pressures that dilate the ventricles, compress and thereby restrict the development of the brain and eventually destroy neurological function.
By the same token a urinary tract malformation and/or obstruction can produce a similar situation in the bladder of the fetus. This condition can cause consequential restriction of the development of the renal and pulmonary systems of the fetus.
In the past, it has been common clinical practice to utilize implanted shunts in adults and children for bypassing a buildup of fluid and fluid pressure from one area of the body to another. In dealing with a fetus, however, use of this type of shunt has been impossible due to its small size. This procedure is greatly complicated by the fact that accessibility to the fetus and the implantation of such a shunt is extremely tenuous. As can be visualized, it is quite difficult to merely miniaturize existing biological shunts in order to attempt to correct the abnormalities which have now been recognized in fetuses. One of the major problems involves the placement of the shunt without creating trauma in the mother or fetus which might cause termination of the pregnancy. One of the best ways found to accomplish this is by the use of a relatively small surgical needle to implant the shunt in the required area of the fetus. However, the use of this needle creates many problems relating not only to size but the actual structure of the shunt which can be implanted by needle.
In addition, many of the problems associated with this field exist because of (1) the inaccessibility of the fetus while in utero, and (2) the inability to completely diagnose the abnormality and to control the implantation of a suitable shunt. The shunt must not only be fail-proof and reliable but capable of fully performing the desired bypassing function. With the shunt installed in the fetus a continuous fluid decompression and prevention of further accumulation is provided which allows a normal growth and development of the body organs and proper development of the nervous system.
The antenatal shunt provided in the present invention addresses these major problem areas and avoids or minimizes some of the antenatal abnormalities which have been very destructive to fetuses in the past.